US Patent 7399988 - Wide temperature range quantum dot photodetector

http://www.freepatentsonline.com/7399988.html

With a rise in temperature quantum dot photodetectors can have a reduction in sensitivity. This patent from Fujitsu teaches a configuration which avoids this problem using a stacked quantum well/embedded quantum dot structure. Claim 1 reads:

1. A photodetecting device having quantum dots, comprising:

a quantum dot structure including a first embedding layer, and quantum dots embedded by said first embedding layer; and

a quantum well structure formed at a location downstream of said quantum dot structure in a direction of flow of electrons which flow perpendicularly to said quantum dot structure during operation of the photodetecting device, said quantum well structure including second and third embedding layers, and

a quantum well layer which is sandwiched between said second and third embedding layers, and whose band gap is smaller than those of said second and third embedding layers.